Materials that absorb up to about 20 times their own weight are well known. U.S. Pat. No. 6,293,935 issued to Kimura et al. (Sept. 25, 2001) teach the use of a wide range of polymeric materials, including starch, crosslinked carboxymethylated cellulose, and polyacrylic acid. Some of the most absorbent materials ever discovered are alkali saponified gelatinized-starch-polyacrylonitrile graft polymers. Examples are discussed in U.S. Pat. No. 3,985,616. (Oct. 12, 1976), U.S. Pat. No. 3,935,099 (Jan. 27, 1976), U.S. Pat. No. 3,981,100 (Sept. 21, 1976), and U.S. Pat. No. 3.997,484 (Dec. 14, 1976), all issued to Weaver et al. Although some of those patents assert that the starch-containing polymer compositions may be able to absorb amounts of water equaling up to more than 1000 times their own weight, such statements in the prior art did not were not borne out in practice. To date, the highest absorbance of fluid has only been about 150 times wt/wt.
Since highly absorbent materials provide increased efficiency and convenience, and reduce cost and environmental waste, there are continuing efforts to provide even higher absorbencies. U.S. Pat. No. 6,439,492 issued to Leiggi (Aug. 27, 2002) teaches an absorbent pad comprising a main enclosure having an absorbing element used to absorb fluids dropped by motor vehicles. Given the amount of fluid that may be dropped from an automobile, it would be helpful to provide greater absorbencies than that taught by Leiggi.
One method of increasing absorbency is to provide materials with numerous activated double bonds. U.S. Pat. No. 5,863,958 issued to Dyer et al. (Jan. 26, 1999). Dyer et al. teach polymers made from 1,3,7-octatriene or like conjugated polyenes, and a crosslinking agent having at least 2 activated double bonds. A preferred product using that technology is ethylene glycol dimethacrylate. Dyer et al. teach that such polymers can be used to make absorbent foams that are useful in articles such as diapers, as well as latexes that are useful as binders and adhesives.
There is, however, no recognized method of activating polymers in general, so that they can achieve very high absorbencies of 250 wt/wt or more.